Revert "third_party: Roll libwebm snapshot."

This reverts commit 74aaa2389ec056f9dd8631eeed42fe7a757daf32. Unstable
under valgrind because of uninitialized reads. Limiting the bad bisect range.

Change-Id: I45b32f0ee0ba45795e7efb9947fb805830c8ce0e
27 files changed